1. Field of the Invention
The present invention relates to front end collision load paths defined by the vehicle frame and other support structures.
2. Background Art
Hinge pillars are the part of a vehicle to which vehicle doors are attached by hinges. Hinge pillars do not normally provide the primary support for the front end structure in the event of a front end collision. The primary support for the front end structure is provided by frame members that define a lower load path and an upper load path.
The lower load path and upper load path are defined by the vehicle frame for analysis of collision energy management and the development of passenger compartment intrusion maps. Intrusion maps simulate vehicle energy absorption in response to collision loads. The upper load path transfers forces to the upper structure of the vehicle that includes the roof structure. The lower load path transfers forces to the lower vehicle structure that includes the rocker.
Roof structures are being developed to meet higher proposed roof crush strength that require the roof structure to be able to support four times the unloaded vehicle weight. One of the changes in vehicle design is to strengthen the A-pillar and hinge pillar joint by forming the cowl side inner panel and hinge pillar from a high strength steel alloy. By strengthening the cowl side inner panel and hinge pillar, roof crush loads are transferred from the A-pillar to the cowl side inner panel and the hinge pillar.
Intrusion into the passenger compartment is monitored at predetermined locations on a vehicle. In a crash test, points located at various locations around the passenger compartment are monitored to analyze crash energy management and to develop intrusion maps. For front end collisions, intrusions are measured at the hinge pillar and are limited to 50 mm. The hinge pillar is located adjacent the instrument panel that is also measured on intrusion maps. Loads transferred to the upper load path are not monitored because they do not generally result in passenger compartment intrusion. In prior art vehicles, application of loads to the hinge pillar area was normally avoided or minimized to reduce intrusion into the passenger compartment.
A front rail extends from the vehicle bumper to the back-up rail that links the front rail to the rocker. The front rail is offset from the rocker and loads applied during a front end collision result in a bending moment located where the back-up rail is connected to the front end of the rocker. The bending moment reduces vehicle energy absorption and may adversely impact intrusion map performance.
There is a need for an improved vehicle frame that enhances intrusion map performance without substantially increasing the weight of the components required for front end collision energy management.